Container load calculator

For a uniform unit of weight w and packed volume v, units that fit = min( floor(P/w), floor(V/v) ), where P = usable payload and V = internal cube; the smaller floor is the binding constraint. Utilisation: weight% = units·w/P, volume% = units·v/V.

Max gross (on the CSC plate) is the heaviest the container may legally weigh; tare is the empty weight; payload = max gross − tare. Typical figures used: 20ft ≈ 21,700 kg / 33 m³, 40ft ≈ 26,730 kg / 67 m³, 40HQ ≈ 26,330 kg / 76 m³.

Dense wire, mesh and fasteners hit the payload ceiling long before the box is full. Example: 25 kg tie-wire coils of 0.02 m³ in a 40HQ → by weight floor(26,330/25) = 1,053, by volume floor(76/0.02) = 3,800 → 1,053 coils, weight-limited, filling 100% of payload but only ~28% of the cube.

The result is cargo payload, not truck-legal weight — road axle/GVW limits (US ~36 t combination, EU 40–44 t) often bind first, so a fully loaded 20ft of steel may be un-truckable. A heavy-tested 20ft rated to 30,480 kg gross can carry ~28 t (vs the 21,700 kg conservative default). It assumes one SKU and ignores floor point-loads and the ~10–20% real stow loss to dunnage and pallet gaps; declare the SOLAS VGM (cargo + tare) for shipping.